1. Field of the Invention
The present invention relates to a scroll-type compressor used, for example, in an automotive air conditioning system. In particular, the present invention relates to a fastening arrangement for a scroll-type compressor by which a center housing, a front housing, and a rear housing, together forming an outer shell of the compressor, can be easily assembled.
2. Description of the Related Art
A known scroll-type compressor has a housing and mating stationary and movable scrolls arranged in the housing. The stationary scroll comprises a base plate portion and a stationary scroll portion integrally formed with and extending from the base plate portion, and the movable scroll also comprises a base plate portion and a movable scroll portion integrally formed with and extending from the base plate portion for engagement with the stationary scroll portion. A self-rotation preventing mechanism is arranged between the housing and the movable scroll to prevent rotation of the movable scroll about its own axis. The drive shaft is rotatably supported in the front part of the housing and has an eccentric shaft portion at the inner end thereof, to which the movable scroll is connected so that the movable scroll can move in a circular orbit around the longitudinal axis of the drive shaft. When the movable scroll moves in an orbit around the longitudinal axis of the drive shaft while the self-rotation of the movable scroll about its own axis is prevented, a refrigerating medium is introduced from the suction chamber into the enclosed compression chamber formed between the stationary and movable scrolls, and compressed as the volume of the compression chamber is reduced, the compressed gas being discharged from the compression chamber into the outlet chamber via the outlet hole provided in the base plate portion of the stationary scroll.
The stationary scroll and the housing of the compressor are usually made separate from each other, as shown in Japanese Unexamined Utility Model Publication (Kokai) No. 1-162094. In this prior art, the stationary scroll is inserted in the housing near the bottom thereof, and fastened to the housing by fastening bolts which are inserted from the rear side of the housing. The movable scroll is then brought into an engagement with the stationary scroll, and the self-rotation preventing mechanism is then positioned to the rear surface of the base plate portion of the movable scroll. The front case is then attached to the front end of the housing and fastened to the latter by fastening bolts which are inserted from the front side of the housing. In addition, a front nose member incorporating the orbital mechanism for the movable scroll therein is attached to the front case and fastened to the latter by further fastening bolts.
In the conventional scroll-type compressor, the inserting direction of the fastening bolts which fasten the stationary scroll to the housing is opposite to the inserting direction of the fastening bolts which fasten the front case to the housing, and so it is necessary to turn the compressor 180 degrees during assembly on the manufacturing line. Therefore, there are the problems that the efficiency of the assembly work is low and that it is difficult to reduce the production cost of the compressor. Also, since the stationary scroll and the housing of the compressor are made separate from each other, the accuracy of the stationary and movable scrolls tends to be low, and the fluid tightness of the compression chamber is reduced, with the result that it is difficult to improve the volumetric efficiency of the compressor.
Another scroll-type compressor, intended for use in a home air-conditioner, has been proposed in Japanese Unexamined Utility Model Publication (Kokai) No. 4-117195 and, in the compressor a plurality of fastening bolts are inserted in the same direction. In this compressor, an electric motor is housed in a motor housing and a compressor unit comprising an end plate and a stationary scroll is attached to the motor housing. In the assembly work, the compressor unit, in which the stationary scroll is fastened to the compressor housing by fastening bolts, is first prepared. The orbital mechanism and the self-rotation preventing mechanism are then arranged at the inlet opening area in the motor housing, and the movable scroll is connected to the output shaft of the motor. The compressor unit is then attached to the compressor housing by more fastening bolts. Since a considerable member of steps are necessary to assemble the compressor, it can be said that the assembly work is not easy. In this case too, the stationary scroll and the end plate which corresponds to a part of the compressor housing are made separate from each other, and, as described above, the fluid tightness of the compression chamber is reduced, with the result that it is difficult to improve the volumetric efficiency of the pump.